The measurement and analysis of the human diaphragm electromyogram (EMGdi), as obtained with an esophageal electrode, requires objective control of the disturbances and filtering effects which can influence the signal. One issue of importance is that an increase in the muscle-to-electrode distance (MEdist) acts as a low-pass filter, filtering out the high frequency components of the EMG power spectrum (the MEdist filter). Due to the numerous factors which can influence the EMGdi, control of signal quality is also of utmost importance. The aims of this study were: (1) to evaluate the effect of the MEdist filter on EMGdi, as measured with a multiple array esophageal electrode, (2) to take advantage of the MEdist filter in order to locate the position of the diaphragm with respect to the electrodes, and (3) to evaluate the influence of changes in chest wall configuration on EMGdi center frequency (CF) values, while controlling for both signal quality and the MEdist filter. / Five normal male subjects performed static contractions of the diaphragm at seven predetermined chest wall configurations. The EMGdi was measured with an array of eight steel rings mounted on a catheter, forming seven sequential pairs of electrodes, with an interelectrode distance of 10 mm. EMGdi signal quality was evaluated by computer algorithms. The pair of electrodes whose EMGdi signals (and power spectrums) were the least influenced by the MEdist filter was assumed to be closest to the diaphragm. / The results of the study indicated (1) EMGdi power spectrums and their associated CF values were strongly affected by the position of the diaphragm with respect to the multiple array esophageal electrode. CF decreased by approximately 1 Hz per mm displacement away from the diaphragm. (2) By controlling for the MEdist filter, there was no relationship found between changes in chest wall configuration and CF values. These data demonstrate that changes in chest wall configuration, and hence diaphragm length, do not influence the CF values of the EMGdi, if the distance between the electrodes and the diaphragm and signal quality are controlled for.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.22536 |
| Date | January 1994 |
| Creators | Beck, Jennifer, 1968- |
| Contributors | Grassino, Alex (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001426045, proquestno: MM00002, Theses scanned by UMI/ProQuest. |
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